Its high time I upgraded my aged TBird 1.33Ghz machine. I'm seriously considering a AMD64 3000+ but I"m a little worried/curious about what I actually get for my money. I've read through some of the forums here and noticed some apps don't compile, and there are a handful of hoops here and there. What if I compile everything in 32bit, do I still get great performance? Can I mix 64 and 32 on the same install? How is 64bit support coming along? Would an XP processor be a better investment, or perhaps an HT enabled P4?

I'm not a developer, more of a power user. Games, MP3/movie encoding, lots and lots of compiling are my normal uses.

I personally opted for the amd64 3000+. The XP at the same price point has similar, if a little worse, performance marks in a pure 32-bit env. so I see it as buying for the future. Plus, you get to beta test all that great 64-bit stuff if that's your thing.

You can safely run a normal 32-bit OS on this hardware. WinXP-32 runs fine and is faster in most benchmarks than a similarly clocked AthlonXP. If you want to go 64-bit, you've got Gentoo on amd64 and beta versions of Server2003 and XP--but I wouldn't suggest any of these for a production environment. I currently boot Gentoo-64 as my primary desktop OS, and use a few 32-bit applications (openoffice-bin, e.g.) without any problems. I also have WinXP-32 on another partition (mostly for gaming and benchmarking).

You can "mix" as long as your OS is 64-bit. That is, you can run 32-bit apps in a 64-bit environment, but not vice versa. However, there are some issues and "early adopter" gotchas like no 64-bit flash plugin for your 64-bit browser. Of course, you could always compile your browser as 32-bit and then use the 32-bit plugin...

I won't get into the Intel vs. AMD argument... My server runs Gentoo on a dually Tualatin.

At this point, if you're even slightly interested in getting involved in the early phases of a 64-bit OS, go with the AMD64. Even if you later find that you don't want to spend much time with this stuff, you can still run a pure 32-bit system with great performance--and you can go to a 64-bit environment when it becomes more stable.

I have no trouble with being an early adopter. I ran ~x86 the second I found it as an option.

Basically, I can compile everything in 64bit if it works, and just use 32bit if not? Meaning, I have most everything compiled in 64bit, but can compile one thing in 32bit and go about my merry business?

Using AMD64, you should switch to OGG. oggenc is unblievable fast on a 64bit system (about 350%, according to some benchmarks, due to the heavy use of 64bit integers).
I don't know about video, but the AMD64 architecture offers an impressive bandwith, maybe you'll see a nice speedup there, too.
Games are the only issue I currently see, but Nvidia's working on some sort of hybrid 64bit/ 32bit driver. Currently, you'll only get direct rendering (hardware accelleration) with 64bit software - 32bit software uses MESA on Linux/ x86-64.

Edit:
Yes, you could mix (add 'multilib' to your USE flags), but most applications _do_ work in 64bit. They are masked only 'cause nobody tried to compile them...

I have no trouble with being an early adopter. I ran ~x86 the second I found it as an option.

Basically, I can compile everything in 64bit if it works, and just use 32bit if not? Meaning, I have most everything compiled in 64bit, but can compile one thing in 32bit and go about my merry business?

Yes... for the most part. For example, you can't build a 64-bit executable that has dependencies on a 32-bit library. So, if you find that libFOO won't compile under 64-bit, you can compile it under 32-bit, but you can't build any 64-bit binaries that link to libFOO. The flash plugin issue I mentioned above is another example--I want to run MozillaFirebird with my optimizations as a 64-bit app, but I can't use flash (nor can I get the mplayer-plugin to work). That's really my biggest issue with usability right now (gaming being the second biggest).

Also, the other issue I hear about regards the binary video formats for mplayer. Since the libraries are closed-source, binary only, you have to use a 32-bit mplayer if you want to use them.

This might be more troublesome... for example, I don't believe that the imap c-client will compile cleanly under amd64, so if you need PHP with IMAP support, you'd have to compile imap as 32-bit... and PHP as 32-bit... and Apache as 32-bit... Just an example. No clue if that's actually the case.

BTW, I hear that the zip compression stuff is MUCH faster under 64-bit for the same reasons, I'd guess, that OGG is.

I'll basically just second what everyone else is saying. I'm using gentoo now, all the stuff is compiled for 64bit, with the exeption of open office and grub. I've been forcing things to emerge with explicit paths, and most of the time they just work, but things aren't completely stable. Mozilla Firebird is occasionally flakey, and my mouse is essentially un-usable when there is heavy processor load. The programs I've had trouble with are marked buggy, and the mouse was three dollars new (dmesg gives constant low level warnings concerning that), so I don't blaim anyone but myself.

The system is, I think, immature. I suspect that things will get substantially faster as gcc gets better at compiling for 64bit systems, as the 2.6 kernel becomes more mature and so on._________________The new scum

Well i bued my ahtlon64 3000+ for 224Euro and mainboard for 85. It has better performance than 3200+ xp , the only thing , that raises the costs was the new mainboard. From this point of view it is worth of money i paid for it (I can say i also baught a pleasure to play with 64 bit linux). On the other side the mainboard is not future-proof cause amd will move to socket 939 and u will have to buy new 939 board to upgrade. I think its worth waiting for them, allthough it can be long (2-3 months), but the prices will fall in much more acceptable range, and the gentoo on amd64 will mature a bit. Anyway the only problem for me in gentoo - i cant get enemy territory to run hardware accelerated under 64 bit gentoo (i have to use windows because i get better framerates and better mouse-handling). But u can still use ur system in 32bit on it. I was able to boot on amd64 from my old linux athlonxp installation without any problems.

How about motherboards? Any particular brands people are using that are working well? I've normally been keen on Asus boards, but I see their AMD64 line uses VIAs chipset. Anyone using an Nforce 3 based board?

Nope, I'm using an AMD chipset (Opteron, Tyan board). And I would recommend it, 'cause I'm really happy with Tyan actively supporting Linux. BTW, if you don't mind to use reg ECC RAM, and wan't to spend a little more, you should consider a Tiger K8W with a single CPU, that way you keep a nice upgrade path...

I'm running the Shuttle AN50R without any problems. I typically go with Asus or Abit as a rule (though my server is a Tyan LE-T), but I wanted an Nforce3 board. It's been very stable so far, and my only gripe is with the aging audio hardware which had a lot of noise no matter what OS/drivers I tried. I had a santa cruz laying around that I dropped in... I'm still working on firewire, and I haven't tried the gigabit port or any power management stuff, but the rest of the hardware is supported and functioning well.

I would recommend ASUS. MSI also has a very nice mainboard, but there seems to be some trouble with getting powernow/cpudyn to work. Most likely that will be remedied in a future bios release, but right now I have some regrets that I couldnt get my hands on an ASUS board. Only ASUS and MSI support the powernow feature, which is a very nice thing to get your systems temperature and noiselevel down.